Conventionally, a powertrain of a vehicle includes a transmission which changes torque and/or the number of rotations of a driving apparatus including, for example, an engine and/or an electric motor, which is used for driving a driving wheel, so that the torque and/or rotations are transmitted to the driving wheel according to running conditions of the vehicle. There are some types of transmissions including, for example, a normally-meshed type transmission. A known normally-meshed type transmission includes plural idler gears, each of which meshes with a rotary shaft connected to the driving wheel to be rotatable relative to the rotary shaft and not to be movable in a direction of a rotational axis, and plural gears, which are provided around a periphery of a counter shaft arranged to be parallel to the rotary shaft. The idler gears and the gears normally mesh with each other. According to the known normally-engaged type transmission, a sleeve is spline-fitted to the rotary shaft to be movable in the direction of the rotational axis, and the sleeve is arranged side by side with the idler gear. Engaging teeth (the spline), which are provided at a joining surface of the sleeve which is joined to the idler gear, are brought to be engaged with engaged teeth (dog clutch teeth), which are provided at a joined surface of the idler gear. Thus, the idler gear engaged with the sleeve and the rotary shaft rotate integrally with each other. As the idler gear which rotates integrally with the rotary shaft and the gear of the counter shaft which meshes with the idler gear rotate in association with each other, torque and/or the number of rotations of the rotary shaft is transmitted to the counter shaft. A shifting operation is performed by selecting, from among the plural idler gears which include different numbers of teeth to each other, the idler gear that is to be rotated integrally with the rotary shaft and by bringing the sleeve into engagement with the selected idler gear.
According to the known transmission, a shift instruction is present at a time of a shifting operation, however, the shifting operation is actually started thereafter and therefore time lag is generated. At the shifting operation, for example, an up-shift operation, the gear (spline) arranged at an input shaft-side is engaged with the gear (the dog clutch teeth) arranged at an output shaft when a rotational speed of the gear of the input shaft-side substantially coincides with a rotational speed of the gear of the output shaft. The gear arranged at the output shaft includes a high gear ratio and rotates at a low rotational speed in accordance with rotations of vehicle wheels. Accordingly, after the shifting operation starts, engine torque needs to be controlled to be reduced and/or a pressing torque of the clutch needs to be controlled, for example. However, these controls are executed in accordance with an actual start of the shifting operation, and therefore it is important at which point of time the start of the shifting operation is determined. According to disclosure related to JPH7-167276A (hereinafter referred to as Patent reference 1), the number of rotations of an input shaft of an automated transmission and the number of rotations of an output shaft of the transmission are obtained, and a gear ratio is calculated from the two rotational speeds. At a time point when change in a value of the gear ratio reaches a predetermined threshold, determination is made that the shifting operation has actually started, and the controls, which are to be executed after the start of the shifting operation, are executed.
However, according to a shift control method described in Patent reference 1, it is determined whether or not the shifting operation has actually started after the predetermined change occurs in the gear ratio value. The gear ratio is a ratio of the number of rotations of the input shaft driven by a drive shaft of an engine relative to the number of rotations of the output shaft driven by a rotation of the wheels. At the time of shifting operation, the shifting operation needs to wait to be performed until the number of rotations of the engine decreases. Therefore, the controls which are to be executed after the determination of the start of the shifting operation may be delayed, and as a result, drivability may be deteriorated and/or a gear shift shock may be generated due to the delay of the controls.
A need thus exists for a dog clutch control apparatus for an automated transmission, which is not susceptible to the drawback mentioned above.